The main purpose of the present project is to advance our understanding of the social interactions of hyperactive children with their parents, how these interactions change with age, and how different doses of stimulant medication (a commonly used treatment for these children) affect these interactions. Several studies are proposed. The first will compare 60 hyperactive children across ages 5 to 9 years with 60 normal children in their interactions with their mothers during a free play and task situation. This should reveal differences between the groups as well as across the different age levels. The second study will examine the effects of 0.3 mg/kg b.i.d. and 0.7 mg/kg b.i.d. of methylphenidate (a stimulant drug) on the mother-child interactions of the 60 hyperactive children. This should reveal how these drugs alter the manner in which these children and their mothers change their social behavior as a result of the medication.